The present invention is directed to a closed system for the metered dispensing of a fluid from a container. A one-way valve is located at the outlet of the system affording flow out of the container while preventing any backflow of contaminants into it. Initially, the container is filled with a fluid free of air or any other gases. The one-way valve maintains the integrity of the fluid throughout its useful life even over extended time periods. The system includes means for selectively dispensing metered amounts of the fluid.
In U.S. Pat. No. 4,846,810, a valve, hereinafter called the RESEAL.RTM. valve, is disclosed for affording one-way flow out of a container while preventing any backflow to the valve which might contain contaminants. Contaminants from outside the valve may be microorganisms, atmospheric gases, not only emptying the container, but also any metering chamber attached to the container. Maintaining the closed system for metered dispensing of the fluid and at the same time dispensing all of the fluid can present problems.
If air is present in the system it may interfere with the flow of the fluid and, in addition, has a deleterious effect on the fluid.
In the past it has been known to provide a dispensing system where the fluid flows from a container or reservoir through a one-way valve into a chamber with the fluid from the chamber being dispensed through another one-way valve. One of the problems in such a system is that air can enter into the container and contaminate the fluid being dispensed. Further, the chamber receiving the fluid from the reservoir cannot be completely emptied, so that a portion of the fluid is retained and exposed to air entering through the system outlet.